The conventional elevator machinery comprises a hoisting motor driving a set of traction sheaves via a gear, the elevator hoisting ropes being passed around the traction sheaves. The hoisting motor, the elevator gear and the set of traction sheaves are commonly placed in a machine room above the elevator shaft. They can also be placed beside or below the elevator shaft. Previously known are also solutions in which the elevator machinery is placed in the counterweight. The use of a linear motor as a hoisting motor for an elevator and its placement in the counterweight are also previously known.
Conventional elevator motors, e.g. cage induction motors, slip-ring motors or d.c. motors, have the advatage that they are simple and their characteristics and the relevant technology have been developed to a reliable level in the course of decades. Moreover, they are advantageous with respect to price. Placement of a conventional elevator machinery in the counterweight is proposed e.g. in U.S. Pat. No. 3,101,130. A drawback with the placement of the elevator motor suggested in this publication is that the counterweight requires a large cross-sectional area in the shaft.
The use of a linear motor as the hoisting motor of an elevator involves problems because the primary or the secondary structure of the motor needs to be as long as the shaft. Therefore, linear motors are expensive to use with elevators. A linear motor application for an elevator, with the motor placed in the counterweight, is presented e.g. in the U.S. Pat. No. 5,062,501. Still, a linear motor placed in the counterweight has certain advantages, e.g. that no machine room is needed and that the cross-sectional counterweight area required by the motor is relatively small.
Another previously known solution is to use a so-called external-rotor motor, in which the rotor is directly attached to the elevator traction sheave. This type of motor construction is proposed e.g. in U.S. Pat. No. 4,771,197. The motor has a fixed shaft and uses separate shaft supports. The motor is gearless. A problem with this construction is that, to produce a sufficient torque, the length and diameter of the motor must be increased, and this is in most cases impossible beceause there is not enough space in the elevator machine room. In the construction presented in U.S. Pat. No. 4,771,197, the length of the motor is further increased by the brake, which is placed by the side of the rope grooves, and it is also increased by the shaft supports.